1. Towards anions laser cooling * Giovanni Cerchiari (e-mail: giovanni@mpi-hd.mpg.de) Elena Jordan Alban Kellerbauer Max-Planck-Insitut für Kernphysik (Saupfercheckweg 1, 69117 Heidelberg, Germany) International Workshop on Antiproton Physics and Technology at FAIR - Nov 2015 1FAIR workshop 2015 - G.Cerchiari

2. Outline Motivations Negative ions and laser cooling Experimental technique Result and cooling scheme 2FAIR workshop 2015 - G.Cerchiari

3. 3 AEGIS antimatter gravity experiment Main goal: Measurement of g with 1% precision on antihydrogen – Production of a bunched cold beam of antihydrogen (100 mK) – Measurement of vertical beam deflection (10 μm drop over 1 m) FAIR workshop 2015 - G.Cerchiari

4. Doppler laser cooling Negative atomic ions atom Spontaneous emission Detuned laser radiation Negative ion Neutral atom Energy Ground Excited 4FAIR workshop 2015 - G.Cerchiari

5. Bound–bound transitions in La − [C. W. Walter & N. D. Gibson, private communication (2014)] Peak 8 EnergyE = 399.42(3) meV Wavelengthλ = 3104.4(2) nm preliminary all peaks unambiguously assigned laser cooling transition identified: 20 [S.M. O’Malley and D.R. Beck, Phys.Rev. A 81,032503 (2010)] 5FAIR workshop 2015 - G.Cerchiari

6. Ion Source Cs La La target [R. Middleton, A Negative-Ion Cookbook, PA 19104 October 1989 (Revised February 1990)] 6FAIR workshop 2015 - G.Cerchiari

7. 7 Apparatus Overall schematic: – Production of anion beam – Mass separation – Spectroscopy FAIR workshop 2015 - G.Cerchiari

8. Spectroscopy technique Continuous anions current and laser beam Collinear interaction between ions and laser beams Detachment of excited state Measurement of neutral particles flux 8 Energy Ground Excited Resonant transition High cross section Non resonant transition Low cross section Electron affinity Neutrals E Faraday-Cup Anions Ion beam Laser Electrostatic deflector MCP FAIR workshop 2015 - G.Cerchiari

9. Spectroscopy technique Continuous anions current and laser beam Collinear interaction between ions and laser beams Detachment of excited states Measurement of neutral particles flux 9 Energy Ground Excited Resonant transition High cross section Non resonant transition Low cross section Electron affinity Neutrals E Faraday-Cup Anions Ion beam Laser Electrostatic deflector MCP FAIR workshop 2015 - G.Cerchiari

10. Neutrals Spectroscopy technique E Channeltron Faraday-Cup Anions Ion beam Laser Electrostatic deflector 10 Energy Ground Excited Resonant transition High cross section Non resonant transition Low cross section Electron affinity Neutrals produce secondary electrons on a gold mirror Secondary electrons are collected and counted The mirror allows for a second laser Ions in motion perceive to different Doppler shifts FAIR workshop 2015 - G.Cerchiari

11. Neutrals Spectroscopy technique Neutrals produce secondary electrons on a gold mirror Secondary electrons are collected and counted The mirror can reflect a second laser on the beam Ions in motion perceive to different Doppler shifts E Channeltron Faraday-Cup Anions Ion beam Laser Electrostatic deflector 11 Energy Ground Excited Resonant transition High cross section Non resonant transition Low cross section Electron affinity Laser FAIR workshop 2015 - G.Cerchiari

12. La − spectroscopy 21 12 E = 5 keV [E. Jordan et al.,PRL 115 (2015) 113001] 12FAIR workshop 2015 - G.Cerchiari

13. La − spectroscopy 21 13 2 measurements for every acceleration energy Frequency at rest extracted from Doppler shifts E = 5 keV 13FAIR workshop 2015 - G.Cerchiari

14. La − spectroscopy Hyperfine spectrum 21 14 3/2 5/2 7/2 9/2 11/2 5/2 7/2 9/2 E = 10 keV A g = 146.8(3) MHzB g = 36(9) MHz A e = 110.6(7) MHzB e = 5(1) MHz where C, D are functions of quantum numbers I, J, F 14FAIR workshop 2015 - G.Cerchiari

15. La − cooling Hyperfine spectrum 21 15 3/2 5/2 7/2 9/2 11/2 5/2 7/2 9/2 E = 10 keV 3/2 5/2 7/2 9/2 11/2 5/2 7/2 9/2 15FAIR workshop 2015 - G.Cerchiari

16. Outlook La − seems to be excellent laser cooling candidate Next steps: – Paul trap to trap and laser-cool La − under construction – Development of sideband generation for existing laser system – Measurement of resonant cross-section 12 16FAIR workshop 2015 - G.Cerchiari

17. Thanks 17FAIR workshop 2015 - G.Cerchiari